This invention relates to the conversion of installed single glazed windows into multiple glazed windows, more particularly to an improved structure and method for affixing an additional pane of glass and a spacer element to an existing window installation so as to create a double glazed unit having a hermetically sealed, insulating airspace between the panes.
Although it has long been recognized that double glazed windows possess much greater insulating ability than single glazed windows, most installations have been provided with single glazing for the sake of economizing on construction costs. But with the rapid rise of the costs of heating and cooling buildings, this economy has proven to be false. Thus, it has become increasingly desirable to convert single glazing to double glazing, not only for improving the insulating properties, but also for the sake of the advantages attained from the addition of a tinted or reflectively coated pane. Unfortunately, removing and discarding existing windows and installing whole double glazed units in their place incurs prohibitive costs for labor and materials.
Accordingly, it is an object of this invention to provide a method and means for quickly and easily converting a single glazed window into a double glazed window by sealing an additional pane of glass to the existing installation. The present invention is specifically adapted to provide easy installation, ready adaptability to any size of window opening or frame construction, superior moisture barrier integrity, and improved structural strength.
Various attempts have been made in the prior art to provide on-site installation of secondary panes of glass, but all suffer from certain shortcomings that have discouraged their use. A typical prior art approach can be seen in U.S. Pat. No. 2,436,037 (Doney) where a rubber gasket serves as both spacer and sealing means. The rubber-to-glass seal utilized therein is a relatively poor moisture barrier, since most natural and synthetic rubbers are somewhat pervious, thus rendering the surfaces of the airspace susceptible to condensation. Rubber is also susceptible to degradation upon exposure to sunlight and weather conditions. Such an arrangement is limited to installation from the outside on relatively deep frames, a distinct disadvantage at many locations, especially on large buildings. Furthermore, sealing difficulties would be encountered at the mitered corner joints called for in Doney. Another prior art approach is shown in U.S. Pat. No. 3,299,591 (Woelk) where a strip of epoxy resin serves as both spacer and sealant. That arrangement provides only a short barrier against moisture penetration, and the epoxy resin, which is apparently required for the sake of high adhesion strength and room temperature curability, is not a reliable sealing material because of its moisture vapor transmissibility and low temperature inflexibility. In order to obtain an attractive appearance, it also appears that specialized extruding or casting equipment for the epoxy would have to be employed at the installation site. A further prior art approach is disclosed in U.S. Pat. No. 3,573,149 (Tibble et al). In that patent, a neoprene composition is melted and cured in situ to effect a seal. Again, the barrier in the path of moisture penetration is short in length, and the curable thermoplastic material required is not noted for its moisture barrier properties. Installation requires the use of specialized electrical equipment at the site and lengthy heating times. The technique is also susceptible to uneven heating which may, in turn, yield uneven sealing.
Add-on glazing devices of a different type can also be seen in the following four U.S. Patents relating to automobile windows:
U.S. Pat. No. 1,777,435 Hogelund " 1,915,098 Kile " 1,945,742 Hilger " 2,098,127 Auger
Each of these references suffers from lack of permanency and integrity of seal, which are required for acceptance in the architectural glazing field. Each employs an unprotected organic spacer which is subject to moisture penetration.